Molding

Materials

 

  • Ecoflex 00-30, Ecoflex 00-35 2-part silicone rubber
  • Smooth-On Sil-Poxy
  • Acrylic sheets for laser cutting (1/4" and 1/8" think)
  • Silicon mold release
  • Pneumatic tubing
  • Smooth-On Skin Tite
  • Syringe, mixing cups, lab gloves, stir stick, pump

 

molding

 

Fabrication Process

 

1. Laser cut the molds from acrylic sheets, one for top layer and one for bottom layer. Assemble and glue the parts.

2. Mix Ecoflex 00-30 part A and B and pour it into the molds. Mold release and vacuum de-bubble are not necessary here because of the materiality of the acrylic mold and silicon rubber. Keep them on a completely flat surface; otherwise the thickness would be uneven. Evenly distribute the silicone and rub off the excess silicone.

3. Leave the silicone to set and cure in about 2 hours. Use a heat lamp to accelerate the process. 

4. Peel off the cured silicone carefully.

5. Assemble the tube into the reserved channels. Use a little amount of uncured Ecoflex 00-30 to glue the top and bottom parts together. Apply some mold release on the thin air channels to prevent them from clogging together. Carefully squeeze out all the air bubbles; otherwise they become the weak point during inflation. Use Ecoflex 00-35 if this process can be done in 2 mins. Wait for the silicon to cure. 

6. Actuate and check for clog and openings. Use a thin rod to pierce clogs and Ecoflex 00-35 to seal openings as needed.

 

Material Test

 

A series of silicone from Smooth-On was tested: Ecoflex 00-20, Ecoflex 00-30, Ecoflex 00-35, Dragon Skin 10 FAST, Dragon Skin FX Pro. The table below compares their key properties. Among them, Ecoflex 00-30 has a low shore hardness which makes it a very stretchable and flexible material. It’s tensile strength and elongation at break is higher than Ecoflex 00-20 so that it’s harder to break while inflated. Its low mixed viscosity comparing to Dragon Skin series makes it easier to mix and pour. From a series of experiments, Ecoflex 00-30 turns out to be the most suitable one for making this mask. Ecoflex 00-35 has the same properties as Ecoflex 00-30, but with very short cure time and an off-white color. This makes it a better candidate for gluing and repairing holes.

 

 

The table compares key properties